Device for voltage regulation for rectifier plants



Jilly 2 1952 i B. sToRsAND 2,604,611

DEVICE FOR VOLTAGE REGULATION FOR RECTIFIER PLANTS Filed March 5. 948'Patented July 22, 1 952 V H g, 6 4,611 I V DEVICE FOR=VOLTAGE REGULATIONFOR.

'. RECTIFIER PLANTS Bjarn'e'StorsaniiQZurich, Switzerland, assignorto '7I Maschinenfabrikf Oerlik'on, S witzerlaniil;a Swiss firm H A s a a lApplication March s, 1948, Serial No. 12,882 v 4 lnfiwitzerland March 5,1947. l

zurich-oerl ikcnr'" 7 Y 7 Claims. (01. 315-143) It is known to obtain inrectifier installations three various voltages by switching thesecondary windings of the rectifier transformer with three one phasepush-pull connections todouble three phase absorption connections andthen by short circuiting the abscrption-reactance coil (also known asthe phaseequaliser coil. or inter-phase transformer) of'which voltage'sthetheoretical no-load values range from 0.9 to 1.17 and 1.35 Ea; Theusefulness of this arrangement is however reduced by the fact that the.switching for changing from 1.17 to 1.35 requires a break in the currentflow. Hence the switch elements for the conversion are subject toconsiderable loads and stresses especially when also theabsorptionreactance coil must be switched.

These difficulties are avoided according to the invention by anarrangement in which the transformer primary is star-connected and whichas a result of the'magnetic connection of each phase an anode conductionperiod of 120 is obtained and in which means are provided which permitthis action tobe mo'difled'jin order to control the period of anode'current fiowand obtain regulation of the voltage It is also an objectof the invention to extend the period of anode conduction by arrangingthe secondary winding of the transformer inv treble one phasepush-pullconnection and by providing a three phase' absorption-reactance coil ofwhich the action can be progressivelymodified by disconnection,shortcircuiting orthe "like. Thereby the conducting period of thefanodescan be varied from 120 to 200-240? and the voltage can be varied from1.17 times the anode voltage to about 0.75 times the anode; voltage.

Another object of the invention is to shorten the period of anodeconduction by arranging an open delta tertiary winding to thetransformer which winding" is adapted to be shortediby. a variableimpedance whereby the] conduction period can be shortened from 120 toabout 60 and the voltage "increased from 1.17 times Ea to 1.35 times Ea.I I v v In the operation of a "rectif er the voltage of the directcurrent is in a predetermined ratio to the voltage of the alternatingcurrent of the transformer. The theoretical value of the direct currentvoltage Ug is as follows;

wherein'Ed is the voltageoi the secondary' windof one anode.

mg of the transformer b etween'the rectifier anode and the zero pointand a the conduction period When employing six anode. and conduction Ug1.35 E 1 l f f; l When employing sixanode'and conduction Ug n" Whenemploying six Ug .90 When employing'six Ug .75 Ea anode andlelltfcon'duction anode- .and'zj240l conduction Therefolfe is. possibleto; va y ng directrent voltage when the conduction periods of th anodesis varied.

The Single figure one" sawin alarmist 6 and 6 represent. two-.switchcsfor short cir-- cuiting the reactor coil 4-. I is a secondary windingand 8 an adjustable impedance. -9 isthe rectifier and I0 theloadconsisting for instance. of an electrochemical series of cells.- 'I

The operation of the device shown is as follows: For; the lowest voltagestep-all switches are open. As a result of the yoke leaka e due to theprimary star connection in this casethe over,- lapping of the phases inthe one phase pushpull connection is about 60 and the voltage is about20 to 25% lower than in normal one phase push-pull connection (Ug=about0.7 Ea). For the next voltage stepthe switch 5 is closed and operationis in the normal one phase push-pull connection (Ug==0.9 Ea; For thethird. step the three. phases of the absorption reactance coil'areshorted by means of the switches Gfthe switch 'with a voltage ar Ug='1.1-'7 En. -Ne'xt the switch 5 can be again closed andppr'a'tionisefiected insimple'six phase connection with-"Ug" -'l.35*Ea. Instead ofthe switches"adjustable impedances can be used so that thisoperation-may be effected with continuous--variation,'and a regulatingrange of 1.35 .to 0.7'that'islgnearly5 H h Switches are shownfor' conrol purposes but or h, nae i -hie.imp da e r ui i e also be usedsuch asfor example avariableoscillatory circuit "consisting of an inductance'L,

application.

4 of a multi-core absorption-reactance coil so that the higher harmonicscan be produced therein.

What I claim is: 1. In a device for regulating the voltage of rectifiershaving six anodes and a single cathode,

a three phase rectifier transformer having a star connected primarywinding and a secondary winding provided with treble one phase pushpullconnections, in which the ends of the three separate secondary phasewindings are connected "to said six anodes, a delta connected tertiaryIn order to avoid having asymmetric voltage curves as a result of thesaturation, two reactance coils are connected in serie'sl whi'ch' arepreferably magnetised in the opposite senses. Also the capacity can bealtered by connecting and disconnecting single components since it,isdesirg able that the impedance can be varied from an inductive valueat the lowest voltages, through the resonance position to a capacitativevalue in order to increase the working. range of the regulation. Thecapacitative components of the tertiary components serve to assistcommutation and tend to increase the direct current'voltage. Reactancecoils alone, with direct current magnetisation, can be used for theswitches. 6; this magnetisation' can be effected indesired manner alsoby the main current in order to efie'ct voltage compensation. 1 I" Alsoonly a part of the regulating range'of this arrangement may be used ifsuch a wide range as about 50% is not necessary; For many installationsit would suflice if the above steps 1.17 to 1.35 were used'i'n whichcase the absorptionreactance coil is omitted andmeans are merelyprovided for controlling the operation of the tertiary winding which isadvantageous for example for railway installations and for constantvoltage supply systems while for high current rectifiers the three lowersteps are of particular The yoke flux (magneticcoupling) can, if theflux path through air is insuflicient, be efiected by means of anadditional magnetic connection;

this is necessary especially for plants which are to function also at alow load. Also a unit consisting of three one phase transformers isparticularly suitable for this purpose. 7 j

The arrangement can'be used in conjunction with known means for voltageregulation such as step switches, induction regulators or grid controldevices. v

Instead of bridging the absorption-reactance coil 4 by the switches B, 6this can also be closed stepwise 'or it may be provided with a secondarywinding I which is progressively shorted by means of a variableimpedance 8.

Besides the above four main voltage steps of 0.7, 0.9, 1.17and 1.35times Ea, corresponding to 240, 180, 120"and'60 of'thetheoretical'conduction period, there still remains the'possibility, whenusing two six phase connections positioned relativelyby 30 one totheother, of obtaining a voltage step of 1.24 times Ea in treble fourphase connection, since from the sixone phase pushpull-systems threefour phase systems can be produced which are coupledby the three coreabsorption-reactance coil already present. This step isespecially,advantageous for electrochemical plants where thestep 1,35;times E (60) gives too high an-anode load g,

It is also possible to obtain thesa result if instead. of the tertiaryyvindingone of the star windings .is short circuited, on itself outside.the

transformer, towards the zero point, bythemean's winding, means adaptedto open and close said tertiary winding, an absorption-reactance coilswitching means adapted to short circuit said absorption-reactance coil.

2. A device according to claim 1, in which said switching means comprisevariable impedances.

3. A device according to claim 1, in which an oscillatory circuit isemployed for closing said tertiary winding.

4. A device according to claim 1, in which an oscillatory circuit isemployed for closing said tertiary winding, at least one of the valuesof L, C and-R in said oscillatory circuit being adjustable to permitthis circuit to be varied from an inductive impedance to a capacitativeimpedance. 5;. In a device for regulating the voltage of rectifiershaving six anodes and a single cathode, a three phase rectifiertransformer having a star connected primary winding and a i secondarywinding provided with treble one phase push-pull connections, in whichthe ends of the three separate secondary phase windings are connected tosaid six anodes, a deltaconnected tertiary winding, means adapted toselectively open and close said tertiary windings, anabsorption-reactance coil for said one phase push-pull connections, andmeans for switching out said absorption-reactance coil in steps.

. 6. In a device for regulatingthe voltage of rectifiers having sixanodes and a single cathode, a three phase rectifier transformer havinga star connected primary winding and a secondary winding provided withtreble one phase pushpull connections, in which the ends ofthe threeseparate secondary phase windings are connected to said six anodes, anabsorption-reactance coil for said one phase push-pull connections, and

means for switching out said absorption-reactance coil in steps, saidlast named means comprising a separate winding arranged on saidabsorption reactance coil and a variable impedance adapts to shortcircuit said separate winding.

7 7. In a three phase rectifier transformer, a star connected primarywinding and a secondary winding provided with treble one phaseconnections in which the ends of'three separate secondary phase windingsare adapted to be connected to six anodes of a rectifier, a delta.connected tertiary winding, and means adapted to open and close saidtertiary winding.

- BJARNE STORSAND.

file of this patent:

[UN TE STATES PATENTS The following references areof record in the

